Energy-efficient idle listening schemes

ABSTRACT

Two methods for energy-efficient idle listening enhancement for WLAN systems are provided. The first method performs a change of operation of a station (STA) from an active mode to an idle listening mode without notifying the change to an access point (AP) associated with the STA. In the idle listening mode, the AP may transmit frames to the STA using a higher bandwidth, but the STA can only sense channels in a lower bandwidth to save energy. The second method transmits a frame to the AP associated with the STA to notify the AP the change of operation of the STA from the active mode to the idle listening mode. In the idle listening mode, the AP may transmit frames to the STA using the lower bandwidth, and the STA can only sense channels in the lower bandwidth to save energy.

TECHNICAL FIELD

Aspects of the present disclosure generally relate to wireless localarea network (WLAN) systems, and more particularly, to energy-efficientidle listening schemes for WLAN systems.

BACKGROUND

IEEE 802.11ac standard can provide high throughput wireless local areanetworks (WLANs) on the 5 GHz frequency band. IEEE 802.11ac standardspecifies 80 MHz and 40 MHz operations for very high throughput (VHT)and high throughput (HT) stations (STAs), respectively. When an STA isassociated with an access point (AP) operated in the 80 MHz bandwidth,the STA normally has to sense channels across the entire 80 MHzbandwidth if the STA is a VHT STA. If the STA is a HT STA, it normallyhas to sense channels across the primary 40 MHz channel. Sensingchannels across the entire 80 MHz bandwidth or the primary 40 MHzchannel often leads to elevated power consumption on the STA. This ispartly because the system on chip (SoC) on the STA may constantly run inhigh-frequency operations.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments and the advantages thereof may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings. These drawings in no waylimit any changes in form and detail that may be made to the describedembodiments by one skilled in the art without departing from the spiritand scope of the described embodiments.

FIG. 1 illustrates an example wireless local area network (WLAN)architecture, in accordance with some embodiments of the presentdisclosure.

FIG. 2 illustrates an example process of an asynchronousenergy-efficient idle listening scheme, in accordance with someembodiments of the present disclosure.

FIG. 3 illustrates an example process of a synchronous energy-efficientidle listening scheme, in accordance with some embodiments of thepresent disclosure.

FIG. 4 illustrates a flow diagram of a method of an asynchronousenergy-efficient idle listening scheme, in accordance with someembodiments of the present disclosure.

FIG. 5 illustrates a flow diagram of a method of a synchronousenergy-efficient idle listening scheme, in accordance with someembodiments of the present disclosure.

FIG. 6 is a block diagram of an example station (STA) that may performone or more of the operations described herein, in accordance with someembodiments of the present disclosure.

DETAILED DESCRIPTION

As described above, under the IEEE 802.11ac standard, when a station(STA) is associated with an access point (AP) operated in the 80 MHzbandwidth, the STA normally has to sense channels across the entire 80MHz bandwidth if the STA is a very high throughput (VHT) STA. If the STAis a high throughput (HT) STA, it normally has to sense channels acrossthe primary 40 MHz channel. Sensing channels across the entire 80 MHzbandwidth or the primary 40 MHz channel often leads to elevated powerconsumption on the STA as compared to sensing the primary 20 MHzchannel. Energy efficiency of the STA can be improved if the carrier orchannel sensing requirement is relaxed. With the relaxed channel sensingrequirement, the STA only needs to sense one or more channels across alower bandwidth such as the primary 20 MHz bandwidth in the 5 GHzfrequency band (herein also referred to as “minimum BW”). Also, the STAcan switch to operate on a higher bandwidth such as the 80 MHz or 40 MHzbandwidth in the 5 GHz frequency band (herein also referred to as “fullBW”) only when necessary.

The examples, implementations, and embodiments described herein canchange operation of an STA from an active mode with a higher bandwidth(e.g., the full BW) to an idle listening mode with a lower bandwidth(e.g., the minimum BW) to save energy of the STA.

FIG. 1 illustrates an example wireless local area network (WLAN)architecture 100, in accordance with some embodiments of the presentdisclosure. As shown in FIG. 1, the network architecture 100 may includean STA 101 and an AP 102. The STA 101 is associated with the AP 102. TheSTA 101 can transmit wireless radio-frequency (RF) signals carrying datapackets (or data messages, frames, etc.) to the AP 102, as indicated byarrow 103. Similarly, the AP 102 can transmit wireless RF signalscarrying data packets (or data messages, frames, etc.) to the STA 101,as indicated by arrow 104. The circle 110 illustrated in FIG. 1 mayrepresent the range of the RF signals transmitted between the STA 101and the AP 102. When the STA 101 and the AP 102 are located within thecircle 110, data can be transmitted wirelessly between the STA 101 andthe AP 102. The STA 101 may be a device that can access the WLAN such asa mobile device or a computer.

Examples, implementations, and embodiments described herein areprimarily described in the context of a WLAN network. In one embodiment,the WLAN architecture 100 may be a WLAN network using IEEE 802.11acstandard. In other embodiments, the WLAN architecture 100 may be a WLANnetwork using other standards such as IEEE 802.11m standard.

FIG. 2 illustrates an example process 200 of an asynchronousenergy-efficient idle listening scheme, in accordance with someembodiments of the present disclosure. In the asynchronousenergy-efficient idle listening scheme, the AP 102 and the STA 101 cancommunicate data while operating in different modes (i.e., asynchronousmodes).

In one embodiment, at block 201, the STA 101 joins a basic service set(BSS). A BSS may be a single AP (e.g., the AP 102) with all associatedSTAs such as the STA 101 and/or other STAs associated with the AP 102.In one embodiment, the STA 101 may join the BSS and sense the BSS infull BW. For example, under IEEE 802.11ac, the STA 101 can join the BSSand operate in an active mode with 80 MHz bandwidth.

At block 202, the STA 101 detects whether there is a long inactiveperiod. In one embodiment, the inactive period can be a predeterminedtime duration. For example, the STA 101 may detect that there was nodata transmitted to the AP 102 and/or no data received from the AP 102for the predetermined time duration. That is, the link between the STA101 and the AP 102 is inactive for a predetermined time duration. Inanother example, the inactive period can be detected based on number ortype of packets transmitted between the STA 101 and the AP 102 for apredetermined duration of time. For example, when the STA 101 detectsthat the number of packets was below a threshold or the packets have aspecific type, the STA 101 can determine that the link between the STA101 and the AP 102 is inactive.

In one embodiment, if the STA 101 does not detect the inactive period,the process 200 goes back to block 201 where the STA 101 continues tosense the BSS in full BW. On the other hand, if the STA 101 detects theinactive period, the process 200 proceeds to block 203. In oneembodiment, at block 203, the STA 101 detects whether there istransmission data (TX data) scheduled to be transmitted to the AP 102.If the STA 101 detects that there is TX data to be transmitted to the AP102, the STA 101 may transmit the TX data to the AP 102, and the process200 goes back to block 201 where the STA 101 continues to sense the BSSin full BW. On the other hand, if the STA 101 detects that there is noTX data to be transmitted to the AP 102, the process 200 proceeds toblock 204.

In one embodiment, at block 204, the STA 101 performs a change ordowngrade of operation mode to save energy. In one embodiment, the STA101 may silently initiate and subsequently perform downgrade of itsoperation mode on physical (PHY) layer and RF from the active mode witha higher bandwidth (e.g., the full BW) to an idle listening mode with alower bandwidth (e.g., the minimum BW). For example, under IEEE802.11ac, the STA 101 can change its operation mode from the active modewith 80 MHz to the idle listening mode with 20 MHz bandwidth. In oneembodiment, the STA 101 does not send a notification to the AP 102 inany form regarding the operation mode change to avoid additionalprotocol cost, i.e., the STA 101 silently performs downgrade of itsoperation mode.

In one embodiment, when performing the change or downgrade of operationmode to save energy, the STA 101 can first change its operation modefrom the full BW (e.g., the 80 MHz) to an intermediate BW (e.g., 40MHz), and then perform another change to change its operation mode fromthe intermediate BW to the minimum BW (e.g., 20 MHz). In anotherembodiment, the STA 101 may change its operation mode from the full BWdirectly to the minimum BW.

In one embodiment, during the downgrade of operation mode (i.e.,downgrade initiated but before it is completed), the STA 101 may detectthat there is data pending to be transmitted to the AP 102. In thissituation, the STA 101 abandons the downgrade process and resumes itsoriginal operation mode, e.g., the active mode with full BW. In anotherembodiment, at block 204, when performing the downgrade of operationmode, the STA 101 does not send notification to the AP 102 to notify theAP 102 the change of the operation mode from the full BW to the minimumBW. In one example, the STA 101 does not send notification to the AP 102to notify the AP 102 the change of the operation mode from the full BWto the intermediate BW, and from the intermediate BW to the minimum BW.

After the downgrade of operation mode is completed at block 204, the STA101 enters the idle listening mode without notifying the AP 102. Sincethe AP 102 does not know that the STA 101 has entered the idle listeningmode with the lower bandwidth, the AP 102 may still transmit data (e.g.,management frames or data frames) to the STA 101 using the higherbandwidth.

In one embodiment, under IEEE 802.11ac, the full BW is 80 MHz includingfour channels. Each of the four channels includes a 20 MHz channel(i.e., a channel with minimum BW). When the STA 101 operates in the idlelistening mode, the STA senses only one of the four channels such as theprimary 20 MHz channel of the four channels. In another embodiment, whenthe STA 101 operates in the idle listening mode, the STA may sense morethan one of the four channels such as the primary 20 MHz channel andanother 20 MHz channel of the four channels.

When the STA 101 operates in the idle listening mode with the lowerbandwidth (e.g., the minimum BW), in one embodiment, the STA 101 detectsan event indicating a need of using the higher bandwidth (e.g., the fullBW) for transmitting data between the STA 101 and the AP 102. In oneembodiment, the event is that the STA 101 receives a request to send(RTS) frame from the AP 102, as shown at block 205. For example, the AP102 transmits the RTS frame using full BW (e.g., using all of the four20 MHz channels) to the STA 101. However, since the STA 101 senses onlyone of the four channels such as the primary 20 MHz channel, the STA 101receives the RTS only on the primary 20 MHz channel. If the STA 101receives the RTS frame from the AP 102 at block 205, the process 200proceeds to block 206.

After receiving the RTS frame from the AP 102 on the 20 MHz channel, theSTA 101 does not transmit a clear to send (CTS) frame to the AP 102, asin conventional systems. Instead, in one embodiment, at block 206, theSTA 101 may transmit one or more null frame with power management (PM)bit set to 1 to the AP 102 using the 20 MHz channel, such as the primary20 MHz channel, sensed by the STA 101. The PM bit is a reserved bitdefined in the IEEE 802.11ac standard. The null frames are also definedin the IEEE 802.11ac standard. The transmitted one or more null frameswith PM bit set to 1 can be used to notify or interpreted by the AP 102that the STA 101 starts to enter low power mode and then the AP 102starts buffering data destined to the STA 101.

After transmitting the one or more null frame with PM bit set to 1 tothe AP 102, in one embodiment, at block 207, the STA 101 performsupgrade of operation mode in response to receiving the RTS frame fromthe AP 102. For example, at block 207, the STA 101 performs the upgradeof its operation mode on PHY and RF from the idle listening mode withlower bandwidth (e.g., the minimum BW) to the active mode with higherbandwidth (e.g., the full BW). In another embodiment, at block 207, theSTA 101 performs the upgrade of its operation mode on PHY and RF fromthe idle listening mode with minimum BW (e.g., 20 MHz) to theintermediate BW (e.g., 40 MHz), and then performs another change of itsoperation mode from the intermediate BW to the full BW (e.g., 80 MHz).

After the upgrade of operation mode is completed at block 207, at block208, the STA 101 transmits another one or more null frame with PM set to0 to the AP 102 using full BW. The transmitted one or more null framewith PM bit set to 0 can be used to notify or interpreted by the AP 102that the STA 101 has exited the low power (idle listening) mode. Oncethe AP 102 receives the one or more null frames, the AP 102 may resumeor start the process of sending buffered data to the STA 101 using fullBW. And the STA 101 may receive the buffered data using full BW, asshown at block 209. When the AP 102 has finished transmitting allbuffered data to the STA 101, the process 200 goes back from block 209to block 201, where the STA 101 starts to sense the link activity withfull BW and prepare to enter the idle listening mode again if conditionis satisfied such as the inactive period is detected again.

On the other hand, if at block 205, the STA 101 does not receive the RTSfrom the AP at block 205, the process 200 proceeds from block 205 toblock 210. At block 210, the STA 101 detects whether another eventindicating a need of using the higher bandwidth (e.g., the full BW) fortransmitting data between the STA 101 and the AP 102 occurred. In oneembodiment, the another event is that the STA 101 detects that it needsto transmit data (management frames or data frames) to the AP 102 usingthe full BW (e.g., using all of the four 20 MHz channels), as shown atblock 210. If the STA 101 does not detect that it needs to transmit datato the AP 102 using the full BW, the process 200 goes back to block 205to continue to detect whether the STA 101 receives an RTS frame from theAP 102.

On the other hand, if at block 210, the STA 101 detects that it needs totransmit data to the AP 102 using the full BW, the process 200 proceedsto block 211. In response to detecting the need to transmit data to theAP 102 using the full BW, in one embodiment, at block 211, the STA 101performs upgrade of operation mode. As described above, in one example,at block 211, the STA 101 performs the upgrade of its operation mode onPHY and RF from the idle listening mode with lower bandwidth (e.g., theminimum BW) to the active mode with higher bandwidth (e.g., the fullBW). In another example, the STA 101 performs the upgrade of itsoperation mode on PHY and RF from the idle listening mode with minimumBW (e.g., 20 MHz) to the intermediate BW (e.g., 40 MHz), and thenperforms another change of its operation mode from the intermediate BWto the full BW (e.g., 80 MHz).

In one embodiment, when performing the upgrade of operation mode, theSTA 101 does not send notification to the AP 102 to notify the AP 102the change of the operation mode. After the upgrade of operation mode iscompleted at block 211, the STA 101 enters the active mode withoutnotifying the AP 102. Since the AP 102 does not know that the STA 101enters the idle listening mode from the initial active mode, and thenreenters the active mode from the idle listening mode, the AP 102 mayassume that the STA 101 is always in the active mode.

When the upgrade of operation mode is completed at block 211, at block212, the STA 101 transmits data to the AP 102 using full BW (e.g., usingall of the four 20 MHz channels). When the STA 101 has finishedtransmitting all data to the AP 102, the process 200 goes back fromblock 212 to block 201, where the STA 101 senses the BSS channel withfull BW and prepare to enter the idle listening mode again if conditionis satisfied such as the inactive period is detected again.

In one embodiment, in order to avoid that the STA 101 frequentlyswitching its operation mode due to data to be transmitted to the AP102, the data may be first buffered in a memory of the STA 101 until thedata reaches a threshold before performing the upgrade of operationmode. For example, each time when the STA 101 detects data to betransmitted to the AP 102, the data can be first buffered in the memoryof the STA 101. In the idle listening mode, the STA 101 may keepincreasing the data buffered in the memory. The volume and/or delayrequirement of the data are checked before the data is buffered. Whenthe volume and/or delay requirement of the buffered data reaches athreshold, the STA 101 will stop data buffering and initiate the upgradeof operation mode. Buffered data is then transmitted to the AP 102 usingfull BW. In this way, buffer overflow or unexpected delay can also beavoided.

FIG. 3 illustrates an example process 300 of a synchronousenergy-efficient idle listening scheme, in accordance with someembodiments of the present disclosure. In the synchronousenergy-efficient idle listening scheme, the AP 102 and the STA 101 cancommunicate data while operating in the same modes (i.e., synchronousmodes). With the synchronous energy-efficient idle listening scheme,there may not be any mismatch between operation modes of the AP 102 andthe STA 101 at any time.

As shown in FIG. 3, in one embodiment, at block 301, the STA 101 joins abasic service set (BSS), similarly as block 201 described above. The STA101 can join the BSS with full BW. For example, under IEEE 802.11ac, theSTA 101 can join the BSS and operate in an active mode with 80 MHzbandwidth. In one embodiment, the 80 MHz bandwidth may be divided intofour channels, each having 20 MHz bandwidth.

At block 302, the STA 101 detects whether there was a long inactiveperiod. Similarly, as block 202 described above, in one embodiment, theinactive period can be a predetermined time duration. In anotherexample, the inactive period can be detected based on number or type ofpackets transmitted between the STA 101 and the AP 102. In oneembodiment, if the STA 101 does not detect the inactive period, theprocess 300 goes back to block 301 where the STA 101 continues to sensethe BSS in full BW. On the other hand, if the STA 101 detects theinactive period, the process 300 proceeds to block 303.

In one embodiment, at block 303, the STA 101 transmits a notificationframe using full BW to the AP 102. The notification frame notifies theAP 102 that the STA 101 will perform a change of operation (i.e.,downgrade of operation mode) from an active mode with a higher bandwidth(e.g., the full BW) to an idle listening mode with a lower bandwidth(e.g., the minimum BW) to save energy. In one embodiment, thenotification frame is an operating mode notification (OMN) action frame,which is defined in the IEEE 802.11ac standard.

At block 304, the STA 101 detects whether an acknowledgment (ACK) signalis received from the AP 102. If the ACK signal is not received by theSTA 101, the process 300 goes back to block 303 to retransmit thenotification frame. If the ACK signal is received by the STA 101, theprocess 300 proceeds to block 305. At block 305, in one embodiment, theSTA 101 transmits one or more null frames with PM bit set to 1 to the AP102 using full bandwidth (e.g., using all the four 20 MHz channels inthe 80 MHz bandwidth). The one or more null frames PM bit set to 1 canbe used to notify the AP 102 to start buffering data destined to the STA101.

At block 306, the STA 101 performs downgrade of operation mode. The STA101 can perform downgrade of its operation mode on physical (PHY) layerand RF from the active mode with a higher bandwidth (e.g., the full BW)to an idle listening mode with a lower bandwidth (e.g., the minimum BW).For example, under IEEE 802.11ac, the STA 101 can change its operationmode from the active mode with 80 MHz to the idle listening mode with 20MHz bandwidth.

In one embodiment, the STA 101 transmits a notification frame such as anOMN action frame using full BW to notify the AP 102 that the STA 101will perform a change of operation from the full BW (e.g., 80 MHz) to anintermediate BW (e.g., 40 MHz). Then the STA 101 performs the change ofoperation from the full BW to the intermediate BW. After the STA 101changes the operation from the full BW to the intermediate BW, the STA101 transmits another notification frame using the intermediate BW tonotify the AP 102 that the STA 101 will perform another change ofoperation from the intermediate BW to the minimum BM (e.g., 20 MHz).Then the STA 101 performs the change of operation from the intermediateBW to the minimum BW.

After the downgrade of operation mode is completed at block 306, the STA101 enters the idle listening mode with a lower bandwidth (e.g., theminimum BW). In one embodiment, the STA 101 transmits one or more nullframes with PM bit set to 0 to the AP 102 using minimum bandwidth (e.g.,using the primary 20 MHz channel of the four 20 MHz channels), as shownat block 307. The one or more null frames with PM bit set to 0 can beused to notify the AP 102 that the STA 101 has entered the idlelistening mode. By doing so, the AP 102 can fully acknowledge that theSTA 101 has entered into the idle listening mode. Thus, the AP 102 maytransmit data (e.g., management frames or data frames) to the STA 101only using the minimum BW. Thus, the STA 101 can transmit and receivedata only using the minimum BW, as shown at block 308.

In one embodiment, when the STA 101 operates in the idle listening mode,the STA senses only the channel in the minimum BW (e.g., the primary 20MHz channel of the four 20 MHz channels in the 80 MHz bandwidth). Inanother embodiment, when the STA 101 operates in the idle listeningmode, the STA 101 may sense more than one of the four channels such asthe primary 20 MHz channel and another 20 MHz channel of the fourchannels.

When the STA 101 operates in the idle listening mode with the lowerbandwidth (e.g., the minimum BW), the STA 101 keeps monitoring an eventindicating a need of using the higher bandwidth (e.g., the full BW) fortransmitting data between the STA 101 and the AP 102, as shown at block309. In one embodiment, the event is that the AP 102 transmits anoperating mode notification frame to the STA 101 in order to transmitdata (management frames or data frames) using the full BW (e.g., usingall of the four 20 MHz channels). For example, the AP 102 may try toreduce the amount of transmit data being buffered for the STA 101. Andthe STA 101 receives the operating mode notification frame only on theprimary 20 MHz channel. In another embodiment, the event is that the STA101 detects that it needs to transmit data (management frames or dataframes) to the AP 102 using the full BW (e.g., using all of the four 20MHz channels). If the STA 101 does not detect the event, the processgoes back to block 308.

If the STA 101 detects the event, the process proceeds to block 310. Atblock 310, in response to the event, in one embodiment, the STA 101transmits one or more null frames with PM bit set to 1 to the AP 102using minimum bandwidth to notify the AP 102 that it will start theupgrade of operation mode. Then the STA 101 performs upgrade ofoperation mode in response to the event, as shown at block 311. Forexample, at block 311, the STA 101 performs the upgrade of its operationmode on PHY and RF from the idle listening mode with lower bandwidth(e.g., the minimum BW) to the active mode with higher bandwidth (e.g.,the full BW). In another example, the STA 101 performs the upgrade ofits operation mode on PHY and RF from the idle listening mode withminimum BW (e.g., 20 MHz) to the intermediate BW (e.g., 40 MHz), andthen performs another change of its operation mode from the intermediateBW to the full BW (e.g., 80 MHz).

After the upgrade of operation mode is completed at block 311, at block312, the STA 101 transmits another one or more null frames with PM setto 0 to the AP 102 using full BW. Then the STA 101 transmits anothernotification frame using full BW to the AP 102, as shown at block 313.The notification frame notifies the AP 102 that the STA 101 has exitedthe idle listening mode and entered the active mode. In one embodiment,the notification frame is an OMN action frame, which is defined in theIEEE 802.11ac standard.

After the AP 102 fully acknowledges that the STA 101 has entered intothe active mode, the AP 102 may communicate data (e.g., managementframes or data frames) with the STA 101 using the full BW. The process300 goes back from block 313 to block 301, where the STA 101 starts tosense the link activity with full BW and prepare to enter the idlelistening mode again if condition is satisfied such as the inactiveperiod is detected again.

In one embodiment, the downgrade or upgrade of operation mode of the STA101 as described with reference to FIG. 2 and FIG. 3 does not impact thelinks between the AP 102 and other STAs associated with the AP 102.

FIG. 4 is a flow diagram of a method 400 of an asynchronousenergy-efficient idle listening enhancement, in accordance with someembodiments of the present disclosure. Method 400 may be performed byprocessing logic that may comprise hardware (e.g., circuitry, dedicatedlogic, programmable logic, a processor, a processing device, a centralprocessing unit (CPU), a multi-core processor, a system-on-chip (SoC),etc.), software (e.g., instructions running/executing on a processingdevice), firmware (e.g., microcode), or a combination thereof. In someembodiments, the method 400 may be performed by the STA 101, or aprocessing device included in the STA 101 (e.g., processing device 602illustrated in FIG. 6).

The method 400 begins at block 401, where the method 400 comprisesdetecting an inactive period. At block 402, the method 400 comprisesperforming a first change of operation of a STA, in response todetecting the inactive period, from a first mode with a first bandwidthto a second mode with a second bandwidth without notifying the firstchange to an AP associated with the STA, wherein the first bandwidth islarger than the second bandwidth. At block 403, the method 400 comprisesdetecting an event, by the STA, indicating a need of using the firstbandwidth for transmitting data between the STA and the AP. At block404, the method 400 comprises performing a second change of operation ofthe STA from the second mode to the first mode in response to the event.

FIG. 5 illustrates a flow diagram of a method 500 of a synchronousenergy-efficient idle listening enhancement, in accordance with someembodiments of the present disclosure. Method 500 may be performed byprocessing logic that may comprise hardware (e.g., circuitry, dedicatedlogic, programmable logic, a processor, a processing device, a centralprocessing unit (CPU), a multi-core processor, a system-on-chip (SoC),etc.), software (e.g., instructions running/executing on a processingdevice), firmware (e.g., microcode), or a combination thereof. In someembodiments, the method 500 may be performed by the STA 101, or aprocessing device included in the STA 101 (e.g., processing device 602illustrated in FIG. 6).

The method 500 begins at block 501, where the method 500 comprisesdetecting an inactive period. At block 502, the method 500 comprisestransmitting, by an STA in response to detecting the inactive period, afirst frame to an AP associated with the STA to notify the AP a firstchange of operation of the STA from a first mode with a first bandwidthto a second mode with a second bandwidth, wherein the first bandwidth islarger than the second bandwidth. At block 503, the method 500 comprisesafter transmitting the first frame, performing the first change. Atblock 504, the method 500 comprises detecting an event indicating a needof using the first bandwidth for transmitting data between the STA andthe AP. At block 505, the method 500 comprises performing a secondchange of operation of the STA from the second mode to the first mode inresponse to the event.

In one embodiment, the asynchronous energy-efficient idle listeningscheme and the synchronous energy-efficient idle listening schemedescribed above can be used for IEEE 802.11ac standard. In otherembodiments, the asynchronous energy-efficient idle listening scheme andthe synchronous energy-efficient idle listening scheme can be used forother WLAN standards where notification frame, e.g. OMN action frame, isnot supported. In one embodiment, the asynchronous energy-efficient idlelistening scheme and the synchronous energy-efficient idle listeningscheme can be used in the 5 GHz frequency band. In other embodiments,the asynchronous energy-efficient idle listening scheme and thesynchronous energy-efficient idle listening scheme can be used in otherfrequency bands such as the 2.4 GHz frequency band or the 6 GHzfrequency band.

FIG. 6 is a block diagram of an example STA 101 that may perform one ormore of the operations described herein, in accordance with someembodiments. In one embodiment, the STA 101 includes a memory 601 and aprocessing device 602. The memory 601 may be synchronous dynamic randomaccess memory (DRAM), read-only memory (ROM)), or other types of memory,which may be configured to store the generated accumulated packets andthe CRC syndrome table, as described above. The processing device 602may be provided by one or more general-purpose processing devices suchas a microprocessor, central processing unit, or the like. In anillustrative example, processing device 602 may comprise a complexinstruction set computing (CISC) microprocessor, reduced instruction setcomputing (RISC) microprocessor, very long instruction word (VLIW)microprocessor, or a processor implementing other instruction sets orprocessors implementing a combination of instruction sets. Processingdevice 602 may also comprise one or more special-purpose processingdevices such as an application specific integrated circuit (ASIC), afield programmable gate array (FPGA), a digital signal processor (DSP),network processor, or the like. The processing device 602 may beconfigured to execute the operations described herein, in accordancewith one or more aspects of the present disclosure, for performing theoperations and steps discussed herein.

In other embodiments, the STA 101 may also include other componentsand/or devices not shown in FIG. 6. For example, the STA 101 may alsoinclude one or more antennas, analog-to-digital converter,demodulator/decoder and/or other components.

Unless specifically stated otherwise, terms such as “receiving,”“generating,” “verifying,” “performing,” “correcting,” “identifying,” orthe like, refer to actions and processes performed or implemented bycomputing devices that manipulates and transforms data represented asphysical (electronic) quantities within the computing device's registersand memories into other data similarly represented as physicalquantities within the computing device memories or registers or othersuch information storage, transmission or display devices.

Examples described herein also relate to an apparatus for performing theoperations described herein. This apparatus may be specially constructedfor the required purposes, or it may comprise a general purposecomputing device selectively programmed by a computer program stored inthe computing device. Such a computer program may be stored in acomputer-readable non-transitory storage medium.

Certain embodiments may be implemented as a computer program productthat may include instructions stored on a machine-readable medium. Theseinstructions may be used to program a general-purpose or special-purposeprocessor to perform the described operations. A machine-readable mediumincludes any mechanism for storing or transmitting information in a form(e.g., software, processing application) readable by a machine (e.g., acomputer). The machine-readable medium may include, but is not limitedto, magnetic storage medium (e.g., floppy diskette); optical storagemedium (e.g., CD-ROM); magneto-optical storage medium; read-only memory(ROM); random-access memory (RAM); erasable programmable memory (e.g.,EPROM and EEPROM); flash memory; or another type of medium suitable forstoring electronic instructions. The machine-readable medium may bereferred to as a non-transitory machine-readable medium.

The methods and illustrative examples described herein are notinherently related to any particular computer or other apparatus.Various general purpose systems may be used in accordance with theteachings described herein, or it may prove convenient to construct morespecialized apparatus to perform the required method steps. The requiredstructure for a variety of these systems will appear as set forth in thedescription above.

The above description is intended to be illustrative, and notrestrictive. Although the present disclosure has been described withreferences to specific illustrative examples, it will be recognized thatthe present disclosure is not limited to the examples described. Thescope of the disclosure should be determined with reference to thefollowing claims, along with the full scope of equivalents to which theclaims are entitled.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”,“comprising”, “includes”, and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. Also, the terms “first,” “second,”“third,” “fourth,” etc., as used herein are meant as labels todistinguish among different elements and may not necessarily have anordinal meaning according to their numerical designation. Therefore, theterminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedsubstantially concurrently or may sometimes be executed in the reverseorder, depending upon the functionality/acts involved.

Although the method operations were described in a specific order, itshould be understood that other operations may be performed in betweendescribed operations, described operations may be adjusted so that theyoccur at slightly different times or the described operations may bedistributed in a system which allows the occurrence of the processingoperations at various intervals associated with the processing.

Various units, circuits, or other components may be described or claimedas “configured to” or “configurable to” perform a task or tasks. In suchcontexts, the phrase “configured to” or “configurable to” is used toconnote structure by indicating that the units/circuits/componentsinclude structure (e.g., circuitry) that performs the task or tasksduring operation. As such, the unit/circuit/component can be said to beconfigured to perform the task, or configurable to perform the task,even when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” or “configurable to” language include hardware—forexample, circuits, memory storing program instructions executable toimplement the operation, etc. Reciting that a unit/circuit/component is“configured to” perform one or more tasks, or is “configurable to”perform one or more tasks, is expressly intended not to invoke 35 U.S.C.112, sixth paragraph, for that unit/circuit/component. Additionally,“configured to” or “configurable to” can include generic structure(e.g., generic circuitry) that is manipulated by software and/orfirmware (e.g., an FPGA or a general-purpose processor executingsoftware) to operate in manner that is capable of performing the task(s)at issue. “Configured to” may also include adapting a manufacturingprocess (e.g., a semiconductor fabrication facility) to fabricatedevices (e.g., integrated circuits) that are adapted to implement orperform one or more tasks. “Configurable to” is expressly intended notto apply to blank media, an unprogrammed processor or unprogrammedgeneric computer, or an unprogrammed programmable logic device,programmable gate array, or other unprogrammed device, unlessaccompanied by programmed media that confers the ability to theunprogrammed device to be configured to perform the disclosedfunction(s).

The foregoing description, for the purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the embodiments and its practical applications, to therebyenable others skilled in the art to best utilize the embodiments andvarious modifications as may be suited to the particular usecontemplated. Accordingly, the present embodiments are to be consideredas illustrative and not restrictive, and the invention is not to belimited to the details given herein, but may be modified within thescope and equivalents of the appended claims.

What is claimed is:
 1. A method, comprising: detecting an inactiveperiod; performing a first change of operation of a station (STA), inresponse to detecting the inactive period, from a first mode with afirst bandwidth to a second mode with a second bandwidth withoutnotifying the first change to an access point (AP) associated with theSTA, wherein the first bandwidth is larger than the second bandwidth,wherein the first bandwidth includes a plurality of channels and thesecond bandwidth includes at least one of the plurality of channels;detecting an event, by the STA, indicating a need of using the firstbandwidth for transmitting data between the STA and the AP, wherein thedetecting the event comprises sensing only the at least one of theplurality of channels included in the second bandwidth and receiving arequest to send (RTS) frame from the AP; in response to the RTS,transmitting by the STA, a first null frame with reserved bit includinga first specified value to the AP; performing a second change ofoperation of the STA from the second mode to the first mode in responseto the event; and transmitting, by the STA, a second null frame with thereserved bit including a second specified value to the AP after thesecond change is complete.
 2. The method of claim 1, further comprisingabandoning the first change if the event is detected before the firstchange is completed.
 3. The method of claim 1, wherein performing thefirst change of operation includes changing operation of the STA fromthe first mode to a third mode with a third bandwidth, and then changingoperation of the STA from the third mode to the second mode, wherein thethird bandwidth is less than the first bandwidth but larger than thesecond bandwidth.
 4. The method of claim 3, wherein performing thesecond change of operation includes changing operation of the STA fromthe second mode to the third mode, and then changing operation of theSTA from the third mode to the first mode.
 5. The method of claim 1,wherein the reserved bit is a power management (PM) bit.
 6. The methodof claim 1, wherein the event indicates a need of using the firstbandwidth for transmitting data from the STA to the AP, and whereinperforming the second change comprises performing the second changewithout notifying the AP.
 7. The method of claim 6, further comprisingbuffering the data in a memory of the STA until the data reaches athreshold before performing the second change.
 8. The method of claim 1,wherein the first bandwidth includes a 40 MHz bandwidth or an 80 MHzbandwidth in a 5 GHz frequency band, and wherein the second bandwidthincludes a 20 MHz bandwidth in the 5 GHz frequency band.
 9. A method,comprising: detecting an inactive period; transmitting, by a station(STA) in response to detecting the inactive period, a first frame to anaccess point (AP) associated with the STA to notify the AP of a firstchange of operation of the STA from a first mode with a first bandwidthto a third mode with a third bandwidth, wherein the first bandwidth islarger than the third bandwidth; after transmitting the first frame,performing the first change of operation; transmitting a second frame tothe AP to notify the AP of a second change of operation from the thirdmode with the third bandwidth to a second mode with a second bandwidth,wherein the third bandwidth is larger than the second bandwidth: aftertransmitting the second frame, performing the second change ofoperation; detecting an event indicating a need of using the firstbandwidth for transmitting data between the STA and the AP; andperforming a third change of operation of the STA from the second modeto the first mode in response to the event.
 10. The method of claim 9,further comprising transmitting a third frame to the AP to notify the APof a completion of the third change.
 11. The method of claim 10, whereinthe first frame and the second frame are operating mode notification(OMN) action frames.
 12. The method of claim 9, wherein performing thethird change of operation includes changing operation of the STA fromthe second mode to the third mode, and then changing operation of theSTA from the third mode to the first mode.
 13. The method of claim 9,further comprising: transmitting a first null frame with a reserved bithaving a first specified value using the first bandwidth to the APbefore performing the first change; and transmitting a second null framewith the reserved bit having a second specified value to the AP usingthe second bandwidth after performing the third change.
 14. The methodof claim 9, wherein the first bandwidth includes a plurality ofchannels, and the second bandwidth includes at least one of theplurality of channels, and wherein detecting the event comprises:sensing only the at least one of the plurality of channels included inthe second bandwidth; and receiving, by the STA, an operating modenotification frame from the AP.
 15. The method of claim 9, furthercomprising: transmitting a first null frame with a reserved bit having afirst specified value using the second bandwidth to the AP beforeperforming the third change; and transmitting a second null frame withthe reserved bit having a second specified value to the AP using thefirst bandwidth after performing the third change.
 16. The method ofclaim 9, wherein the first bandwidth includes a an 80 MHz bandwidth in a5 GHz frequency band, and wherein the second bandwidth includes a 20 MHzbandwidth in the 5 GHz frequency band.
 17. A method, comprising:detecting an inactive period; transmitting, by a station (STA) inresponse to detecting the inactive period, a first frame to an accesspoint (AP) associated with the STA to notify the AP of a first change ofoperation of the STA from a first mode with a first bandwidth to asecond mode with a second bandwidth, wherein the first bandwidth islarger than the second bandwidth; transmitting a first null frame with areserved bit having a first specified value using the first bandwidth tothe AP before performing the first change; after transmitting the firstframe, performing the first change; transmitting a second null framewith the reserved bit having a second specified value to the AP usingthe second bandwidth after performing the first change; detecting anevent indicating a need of using the first bandwidth for transmittingdata between the STA and the AP; and performing a second change ofoperation of the STA from the second mode to the first mode in responseto the event.
 18. The method of claim 17, wherein the first bandwidthincludes a 40 MHz bandwidth or an 80 MHz bandwidth in a 5 GHz frequencyband, and wherein the second bandwidth includes a 20 MHz bandwidth inthe 5 GHz frequency band.
 19. The method of claim 17, wherein the firstbandwidth includes a plurality of channels, and the second bandwidthincludes at least one of the plurality of channels, and whereindetecting the event comprises: sensing only the at least one of theplurality of channels included in the second bandwidth; and receiving,by the STA, an operating mode notification frame from the AP.